This is a 22-year-old woman, G1 P0 with an unremarkable personal or familial history.

Her first ultrasound scan was performed at 13 weeks (nuchal translucency = 1 mm, CRL = 72 mm). The triple was 1:1500. At 22 weeks, ultrasound findings seemed to be normal.

At 30 weeks, the kidneys were hyperechoic, but we could observe normal cortico-medullar differentiation (Figure 2, 3). At 31 weeks, the same anomalies were confirmed. Futhermore, we observed physiological scrotal hydrocele (Figure 4) and a echogenic foci on mitral valve without cardiac dysmorphology (Figure 5-10).

An amniocentesis was proposed and done. Trisomy 13 was diagnosed due to the fetal karyotype. We were really surprised, because the fetus did not have any typical anomaly. After multidisciplinary discussion, we decided to perform a cordocentesis to exclude mosaic trisomy 13.

At 35 weeks, the same anomalies were confirmed without intrauterine growth restriction. The face seemed normal without hypotelorism. The brain and ear were normal. According to us, the extremities of the limbs were normal.

The final karyotype result was trisomy 13. The parents decided to continue her pregnancy. The patient delivered normally at 39 weeks. The baby had an abnormal postnatal adaptation with oxygen therapy. We found that the baby has six fingers with normal feet.

We analyzed again our 3D scanning of hands. On the picture 11, we should have well observed six fingers and the picture 13, 14 showed the abnormal 6th finger but thumb. We should have focused more on the six fingers.